This invention relates to vanadium catalysts for olefin polymerization supported on a phosphate containing base.
Vanadium compounds display catalytic activity in a number of diverse chemical reactions. Since vanadium is closely related to both chromium and titanium in the Periodic Table, it is only natural that it has been tried in place of chromium or titanium as a catalyst for the polymerization of mono-1-olefins, such as ethylene. Peters et al, U.S. Pat. No. 3,371,079 discloses silica supported vanadium pentoxide with a cocatalyst for polymerizing ethylene. Kerby, U.S. Pat. No. 3,271,199 discloses aluminum phosphate supported vanadium pentoxide as a hydrogenation catalyst and suggests aluminum phosphate as a support for chromium or molybdenum for polymerizing ethylene and propylene. However, vanadium catalysts have not been as commercially successful as titanium or chromium catalysts for olefin polymerization. Supported vanadium catalysts have been particularly disappointing as olefin polymerization catalysts. To a substantial extent, the greatest success with vanadium in the prior art as an olefin polymerization catalyst has been in systems more analogous to unsupported titanium systems, i.e., VOCl.sub.3, VCl.sub.4 or VCl.sub.3 used with a reducing agent such as an aluminum hydride. However, the natural tendency of vanadium to catalyze reactions other than polymerization has been a constant problem limiting its usefulness in olefin polymerization.
It would be desirable for some applications to produce polymer having different characteristics from that produced with the chromium systems, such as for instance, polymer with a lower vinyl content and/or a broader molecular weight distribution. Also, it would be desirable to be able to obtain in nontitanium systems the molecular weight sensitivity to hydrogen displayed by titanium catalyst systems.